Pressurized dispensing container



p 7, 1966 A. LIVINGSTONE PRESSURIZED DISPENSING CONTAINER Original FiledNov. 16, 1962 INVENTOR a 0 4)? um asmvi United States Patent 3 275,200PRESSURIZED DFSPENSING CONTAINER Alexander Livingstone, Washington,N.J., assignor to American Can Company, New York, N.Y., a corporation ofNew Jersey Original application Nov. 16, 1962, Ser. No. 238,208. Dividedand this application Dec. 14, 1964, Ser. No.

4 Claims. (Cl. 222389) thereof an imperforate cup-shaped piston mountedin an inverted position and so sized with respect to the inner diameterof the container that product in the upper chamber forms a thin filmbetween the piston skirt and container side wall for purposes ofproviding a lubricant to facilitate piston movement and also a sealantto prevent escape of propellant in the lower chamber around the pistonand into the product chamber. While a pressure can of the foregoingcharacter functions most effectively with many products, diflicultieshave been encountered from a transmigration standpoint with certainother products.

To explain, :a product having a low viscosity or a consistency whichresembles that of water gravitationally bypasses the piston and at leasta portion thereof mixes with the propellant in the lower chamber,producing unsatisfactory results. Then too, the reverse situation occurswith some substances having particular lubricity, viscosity andpenetrating properties. Exemplary thereof are certain petrolatum-basematerials typified by hair grooming waxes, and in the case of this typeproduct the propellant often by-passes the piston, expands within theproduct and destroys the clear or translucent appearance thereof withthe result that product identification is lost.

It is accordingly an important aim of the present invention to provide apressurized dispensing container featuring therein means preventingadmixture of product and propellant.

Another object of this invention lies in the provision of a pressure canof the character which employs interiorly thereof a freely movablepiston and which has associated therewith an annular seal memberpreventing prodnot and propellant from leaking between the piston andcan side walls.

Still another object of the instant invention is to provide apressurized container for dispensing applications having a free movingpiston therein which features barrier means separably or integrallyassociated therewith to prevent propellant and product by-pass.

A further object of this invention lies in the provision of a dispensingcontainer including a tubular body sealed at opposite ends and mountingvalve means at one of said ends, an imperforate generally cup-shapedpiston mounted in an inverted position Within said body and movabletherein, said piston dividing the interior of said body into a productchamber and a propellant chamber, and barrier means between said pistonand said body preventing product and propellant admixture.

Other objects and advantages of the invention will become more apparentas the description proceeds, particularly when taken in connection withthe accompanying drawings.

In the drawings, wherein like numerals are employed to designate likeparts throughout the same:

FIGURE 1 is .a side elevational view, with parts there of taken insection, showing :a pressure can constructed in accordance with theprinciples of this invention; and

FIGURES 2 and 3 are fragmentary elevational views with portions there-ofin section illustrating further exemplary embodiments of the invention.

Designated generally in FIGURE 1 by the numeral 10 is a pressurizeddispensing container, shown as comprised of a tubular metal body 11 towhich is attached by conventional seaming techniques upper and lower endclosures 12 and 13, respectively. Mounted in the center of the upperclosure is valve means 14 which is of conventional construction andaccordingly is not shown in detail. The opposite end closure, on theother hand, has a central opening 15 which is closed afterpressurization of the container by a plug member 16, again in a mannerknown to the art.

Interiorly of the can body 11 there is freely or floatingly mounted apiston member 18, which divides the space therewithin into chamber 21for containing product 22 and a chamber 23 housing propellant 24. Thepiston 18 is constructed of a relatively flexible material which isessentially inert to chemical substances, and one of the polyolefinssuch as polyethylene may be used. The piston is desirably cup-shaped oressentially dome-like in configuration and has an end wall 25 which maybe centrally recessed as at 19 for receiving valve part 17, therebyassuring that maximum upward piston travel can take place andessentially all of the contained product is dispensed.

The piston 18 is further characterized as to shape by a smoothly curvedor rounded shoulder portion 26 and a slightly outwardly flaringdepending skirt portion 27 normally dimensioned slightly smaller thanthe inner diameter of the can body 11 so as to provide an annular space28 between the maximum diameter portion of the skirt and the can bodyinner diameter. Thereby, in accordance with the prior art teachings, athin film of product would extend at least part way down between thepiston skirt 27 and adjacent portion of the can body side wall so as tolubricate the piston as it moves upwardly after valve 14 is opened, andto also provide a seal against propellant transmigration into theproduct chamber 21.

However, as was earlier noted, low viscosity products may actually leakpast the piston skirt into the propellant chamber, and conversely,propellant may by-pass the skirt portion and infuse the product inchamber 21. In

either situation, a package of little, if any, commercial appealresults.

Each of these problems which has plagued the prior art is hereineffectively overcome by barrier means, designated at 30 in FIGURE 1, 40in FIGURE 2 and 50 in FIGURE 3. The barrier means or annular seal may beeither separable from or integral with the piston 18, but in either casepreferably is located along the radius of the arcuate piston shoulderportion 26, 26a or 26b, as appears respectively in the three viewspresented.

The form of barrier member or sealing annulus designated at 30 in FIGURE1 may be provided by a ring of a substance having the properties ofnon-adherency to the piston and container side wall, sufiicient strengthso as to avoid fracture or disintegration during use, and a relativelylow coeflicient of friction in order that it may slide relatively easilyalong the container side wall and thereby not impede piston movement.Desirably the ring barrier 30 should be capable of formation in situ,and this and the other mentioned characteristics are adequatelyfulfilled by a petroleum wax. Many petroleum waxes may be foundsuitable, but preferably the Wax is of the microcrystalline type and inwork conan eflicient sealing action.

ducted to date the microcrystalline wax should be modified by a paraflinwax, zinc or aluminum stearate, or a silicone in order to impart thedesired lubricity.

As a specific example, good results are obtained when themicrocrystalline wax such as polyisobutene has a capillary melting pointbetween 186l94 F., a congeal point of about 186 F., a density of 0.789gr./cm. at 200 F., a melt viscosity of 0.19 to 0.26 poises at 200 F. anda flexibility of 45 to 60 as measured against a standard of 100 for avery flexible wax and for a very brittle wax. An illustrative modifierfor microc-rystalline wax having the named properties is a paraflin waxhaving a capillary melting point of about 138 to 140 F., a congeal pointof about 136 F., a density of 0.765, a melt viscosity of 0.05, and aflexibility of about 50, the density, viscosity and flexibility of theparaflin wax being determined against the same standards as for themicrocrystalline wax. An exemplary amount of paraffin wax modifier isabout 5% by weight based on the total weight of microcrystalline wax.

After formulation in the approximate amounts indicated the wax in moltencondition is poured through the upper open end of the can body 11 priorto filling of the product and propellant therein and with the endclosure 12 removed. The molten wax is directed toward the gap betweenthe can side wall and radius of the arcuate shoulder portion 26 of thepiston 18, and shortly thereafter hardens to a relatively firm statefree of bonded contact with the container side wall and freely slidablethereon. The wax ring 30 forms a cross-section which is substantiallyround, and after the container is filled and charged, actuation of thevalve 14 causes upward piston movement and corresponding travel of thebarrier member in scalable relation between product and propellant sothat no transmigration in either direction can occur, and yet there isno noticeable interference with free piston movement. Further, in commonwith the other forms of the invention, the barrier member performs agentle wiping action on the container side wall and thereby assures thatlittle product residue remains in the container upon completion ofpiston travel.

In substitution for the formed-in-place barrier means 30 of FIGURE 1,the separable type of sealing annulus of this invention may be of thecharacter indicated at 40 in FIGURE 2. As shown therein, the ring isconstructed of a suitable plastic material, and a thermoplastic such aspolyethylene is presently preferred. Desirably, the polyethylene of thering member 40 is of lesser density than that of the piston 18a. Thebarrier means 40 may be semi-circular in cross-section, or semiround asshown, and may have other shapes appropriate to If a semi-circularcross-section is selected, its radius when inserted may be less than asillustrated so that when the container is pressurized the sealing ringwill flare outwardly and provide the desired constant sealing action.

It is also within the contemplation of this invention that the barriermember be integral with the freely movable piston, and in somesituations this may be the preferred construction. An illustrativeembodiment thereof appears in FIGURE 3, wherein the sealing annulus isdesignated by the numeral 50. It is to be observed that' the barrier 50is disposed at the radius of the arcuate shoulder portion 26b of thepiston 18b and is generally normal thereto, extending upwardly andoutwardly from said radius. Desirably, the barrier member is tapered incross-section so as to provide a relatively thin wiping edge 51 while atthe same time effectively blocking any by-pass of product into thepropellant chamber, or the reverse. The wiper-seal member 50 is formedintegral with the piston body during the molding thereof, and the edgeportion 51 exerts a gentle force on the container side wall by reason ofbeing slightly over-sized with respect to the inner diameter thereof. Nosubstantial product residue thus remains upon completion of pistontravel, and an impervious bridge further spans the gap between thepiston and container side wall to prevent bypass of product andpropellant.

Various forms of barrier means have been disclosed herein, and these andother modifications may of course be effected without departing from thenovel concepts of the instant invention.

I claim:

1. A dispensing container, comprising a tubular body sealed at oppositeends and mounting valve means at one of said ends, an imperforategenerally cup-shaped piston mounted in an inverted position within saidbody and movable therein, said piston dividing the interior of said bodyinto a product chamber and a propellant chamber, and a relativelyflexible annular wax seal member freely received between said piston andsaid body and not connected to said piston or said body preventingproduct and propellant admixture.

2. A pressurized dispensing container, comprising a tubular metal body,closure means at opposite ends of said body, dispensing means mounted byone of said closure means, an imperforate generally dome-shaped flexiblepiston received in said body and having an end wall and a downwardlyextending skirt wall, said skirt wall being out of engagement over amajor portion of its surface with said body and having an annularportion extending inwardly to create an annular recess between said bodyand said piston, said piston dividing the interior of said body into aproduct chamber and a propellant chamber, and a relatively flexibleannular seal member disposed within said recess and in contact with butnot adhered to or formed integral with said skirt wall, said annularseal member being in sliding contact with said tubular body along anannular line of contact for preventing product and propellant admixture.

3. A pressurized dispensing container as defined in claim 2 wherein saidannular seal member has a semi-circular cross-section.

4. A pressurized dispensing container as defined in claim 2 wherein saidseal member has a circular crosssection.

References Cited by the Examiner UNITED STATES PATENTS 2,459,743 l/ 1949Trainer et al 2223 89 X 2,826,339 3/1958 Maillard 222387 X 2,925,9372/1960 Schmidt 222389 X 3,066,836 12/1962 Trumbull 222327 3,179,3094/1965 Cope 222389 ROBERT B. REEVES, Primary Examiner.

STANLEY H. TOLLBERG, Examiner.

1. A DISPENSING CONTAINER, COMPRISING A TUBULAR BODY SEALED AT OPPOSITEENDS AND MOUNTING VALVE MEANS AT ONE OF SAID ENDS, AN IMPERFORATEGENERALLY CUP-SHAPED PISTON MOUNTED IN AN INVERTED POSITION WITHIN SAIDBODY AND MOVABLE THEREIN, SAID PISTON DIVIDING THE INTERIOR OF SAID BODYINTO A PRODUCT CHAMBER AND A PROPELLANT CHAMBER, AND A RELATIVELYFLEXIBLE ANNULAR WAX SEAL MEMBER FREELY RECEIVED BETWEEN SAID PISTON ANDSAID BODY AND NOT CONNECTED TO SAID PISTON OR SAID BODY PREVENTINGPRODUCT AND PROPELLANT ADMIXTURE.